I agree, let him do his thang. If you look at the options, it makes sense.
1. Let him do his thing, and everything works.2. Let him do his thing, he did something wrong, it's on him to fix it because he did it his way.3. Do it your way, and have everything take twice as long, if it ends up working, then Hooray, but it took 5 years to do it, and if it doesnt work, then you're stuck with no help, and a car that doesn't run.
I wish I had a know-it-all mechanic uncle. Consider yourself lucky.
